Just one week removed from a two-touchdown game and just two weeks removed from a 20-carry game, Chris Ivory gained a measly 22 yards on eight carries Week 9 at Kansas City. Change-of-pace option Chris Johnson was better, gaining 69 yards on 11 carries and 32 on two catches, but he got his usual allotment of touches. If not for a couple big plays -- specifically, a 21-yard run in the second quarter and a 26-yard catch in the third, his performance would have been just as forgettable.
It's further evidence that you have no way to predict how either player will perform in a given week. For Ivory, it depends on both the score of the game (Week 7 was a rare close one for the Jets) and whether or not the Jets get inside the 5-yard line (which they rarely do). For Johnson, it depends whether or not he breaks a long one, which is especially unpredictable on a limited number of touches.
It's why I don't care to start either of running back in a standard 12-team league. In anything deeper, you may not have a choice, but Ivory and Johnson are just too unreliable for Week 10 against Pittsburgh.